In recent years, information processors such as a server computer and a personal computer use a disk array technique to virtually handle a plurality of auxiliary storages as a single storage in order to improve disk access speed and to protect stored data. Various methods have been devised for the disk array technique. Representative methods are RAID0 and RAID1.
RAID0 is also called striping. It is a method of dispersing data on a block unit basis to a plurality of auxiliary storage devices, thereby improving disk access speed. For RAID0, at least two auxiliary storages are necessary. On the other hand, RAID1, called mirroring, is a method of writing the same data simultaneously to a plurality of auxiliary storage devices to protect stored data. For RAID1, at least two auxiliary storage devices are necessary in a manner similar to the above. Hereinafter, the function of the RAID0 will be called the RAID0 mode, and the function of the RAID1 will be called the RAID1 mode.
In some cases, depending on the data handled, data is sorted into data emphasized with access speed and data emphasized with protection.
To realize this, there is an information processor that switches between the RAID0 mode and the RAID1 mode using at least four auxiliary storage devices; two auxiliary storage devices dedicated to the RAID0 mode, and two auxiliary storage devices dedicated to the RAID1 mode.
Another technique called matrix RAID is also disclosed. In the matrix RAID, two auxiliary storage devices can be switched between the RAID0 mode and the RAID1 mode depending on data handled. A storage area constructed in the RAID0 mode and a storage area constructed in the RAID1 mode are mixedly exist.